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<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.examples.copy"></a><a class="link" href="copy.html" title="An Optimized Version of std::copy">An Optimized Version
      of std::copy</a>
</h3></div></div></div>
<p>
        Demonstrates a version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">copy</span></code>
        that uses <code class="computeroutput"><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a></code>
        to determine whether to use <code class="computeroutput"><span class="identifier">memcpy</span></code>
        to optimise the copy operation (see <a href="../../../../examples/copy_example.cpp" target="_top">copy_example.cpp</a>):
      </p>
<pre class="programlisting"><span class="comment">//</span>
<span class="comment">// opt::copy</span>
<span class="comment">// same semantics as std::copy</span>
<span class="comment">// calls memcpy where appropriate.</span>
<span class="comment">//</span>

<span class="keyword">namespace</span> <span class="identifier">detail</span><span class="special">{</span>

<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">I1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">I2</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">b</span><span class="special">&gt;</span>
<span class="identifier">I2</span> <span class="identifier">copy_imp</span><span class="special">(</span><span class="identifier">I1</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I1</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">I2</span> <span class="identifier">out</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="keyword">bool</span><span class="special">,</span> <span class="identifier">b</span><span class="special">&gt;&amp;)</span>
<span class="special">{</span>
   <span class="keyword">while</span><span class="special">(</span><span class="identifier">first</span> <span class="special">!=</span> <span class="identifier">last</span><span class="special">)</span>
   <span class="special">{</span>
      <span class="special">*</span><span class="identifier">out</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">first</span><span class="special">;</span>
      <span class="special">++</span><span class="identifier">out</span><span class="special">;</span>
      <span class="special">++</span><span class="identifier">first</span><span class="special">;</span>
   <span class="special">}</span>
   <span class="keyword">return</span> <span class="identifier">out</span><span class="special">;</span>
<span class="special">}</span>

<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="identifier">T</span><span class="special">*</span> <span class="identifier">copy_imp</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">first</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">out</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">&amp;)</span>
<span class="special">{</span>
   <span class="identifier">memmove</span><span class="special">(</span><span class="identifier">out</span><span class="special">,</span> <span class="identifier">first</span><span class="special">,</span> <span class="special">(</span><span class="identifier">last</span><span class="special">-</span><span class="identifier">first</span><span class="special">)*</span><span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">T</span><span class="special">));</span>
   <span class="keyword">return</span> <span class="identifier">out</span><span class="special">+(</span><span class="identifier">last</span><span class="special">-</span><span class="identifier">first</span><span class="special">);</span>
<span class="special">}</span>


<span class="special">}</span>

<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">I1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">I2</span><span class="special">&gt;</span>
<span class="keyword">inline</span> <span class="identifier">I2</span> <span class="identifier">copy</span><span class="special">(</span><span class="identifier">I1</span> <span class="identifier">first</span><span class="special">,</span> <span class="identifier">I1</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">I2</span> <span class="identifier">out</span><span class="special">)</span>
<span class="special">{</span>
   <span class="comment">//</span>
   <span class="comment">// We can copy with memcpy if T has a trivial assignment operator,</span>
   <span class="comment">// and if the iterator arguments are actually pointers (this last</span>
   <span class="comment">// requirement we detect with overload resolution):</span>
   <span class="comment">//</span>
   <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special">&lt;</span><span class="identifier">I1</span><span class="special">&gt;::</span><span class="identifier">value_type</span> <span class="identifier">value_type</span><span class="special">;</span>
   <span class="keyword">return</span> <span class="identifier">detail</span><span class="special">::</span><span class="identifier">copy_imp</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">last</span><span class="special">,</span> <span class="identifier">out</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/has_trivial_assign.html" title="has_trivial_assign">has_trivial_assign</a><span class="special">&lt;</span><span class="identifier">value_type</span><span class="special">&gt;());</span>
<span class="special">}</span>
</pre>
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      Frederic Bron, Steve Cleary, Beman Dawes, Glen Fernandes, Aleksey Gurtovoy,
      Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander
      Nasonov, Thorsten Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert
      Stewart and Steven Watanabe<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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